In electrical/electronic components such as quartz crystal units, IC packages and image display devices (for example, plasma display panels and liquid crystal display panels), encapsulation or sealing (hereinafter collectively referred to as sealing) is conducted by applying and firing a glass frit for sealing or a glass paste for sealing. Furthermore, in many electrical/electronic components such as solar battery panels, image display devices, laminated capacitors, quartz crystal units, LEDs (light-emitting diodes) and multilayer circuit substrates, a patterned electrode and/or wiring (hereinafter referred to as an electrode/wiring) is/are formed by printing an electroconductive glass paste in which a glass powder and metal particles are mixed on a substrate and firing the electroconductive glass paste.
A glass frit for sealing is a mixture of a so-called low melting point glass composition (for example, a glass composition having a low deformation point and a low softening point) and an oxide filler material, and an electroconductive glass paste is a mixture of a low melting point glass composition, metal particles (for example, silver particles, copper particles, aluminum particles and the like), an oxide filler material, a resin binder and a solvent. A glass composition used for a glass frit for sealing or an electroconductive glass paste is soften and flowed during firing to thereby play roles in tightly attaching elements to be sealed to each other and in tightly attaching an electrode/wiring to a substrate. As a glass composition, lead glass (glass comprising lead oxide as a major component), which is soften and flowed at a low temperature and is thermally and chemically stable, was once used.
However, in the industries of electrical/electronic devices, the trends of green procurement and green designing are strong worldwide in recent years, and safer materials are desired. For example, in Europe, the directive on the restriction of the use of certain hazardous substances in electronic/electrical devices by European Union (EU) (RoHS directive) has been in force since Jul. 1, 2006. Lead (Pb) is designated as a prohibited substance of the RoHS directive, and thus there has been a problem that glass comprising PbO as a major component cannot accommodate the RoHS directive. Therefore, various glass compositions free from lead components (lead-free glass) and glass frits for sealing and electroconductive glass pastes using the glass compositions have been studied.
For example, PTL 1 (JP 2010-184852 A) discloses a low melting point glass composition comprising 45 to 65% by weight of V2O5, 10 to 20% by weight of P2O5, 10 to 25% by weight of TeO2, 5 to 15% by weight of Fe2O3, and 0 to 10% by weight of MnO2, ZnO, WO3, MoO3 and BaO in total, in terms of oxides of the components in the glass composition, and being substantially free from lead, bismuth and antimony. According to PTL 1, it is considered that a low melting point glass composition having a softening point of 380° C. or less can be provided, and that the firing temperatures of a glass frit for sealing and an electroconductive glass paste using the glass composition can be 400° C. or less.
PTL 2 (JP 2009-209032 A) discloses a glass composition comprising 33 to 45% by weight of V2O5, 22 to 30% by weight of P2O5, 5 to 15% by weight of MnO, 10 to 20% by weight of BaO, 0 to 8% by weight of R2O (wherein R is an alkali metal element), and 0 to 10% by weight of Sb2O3, TeO2, ZnO, SiO2, Al2O3, Nb2O5 and La2O3 in total, in terms of oxides of the components in the glass composition, and being substantially free from lead and bismuth. According to PTL 2, it is considered that a glass composition that can be softened at a highly practical low temperature (500° C. or less) without using lead and bismuth can be provided.
PTL 3 (JP 2006-342044 A) discloses a vanadium phosphate-based glass having a glass composition comprising 10 to 60% of V2O5, 5 to 40% of P2O5, 1 to 30% of Bi2O3, 0 to 40% of ZnO, 0 to 40% of TeO2, 0 to 20% of R2O (wherein R is Li, Na, K, Cs) and 0 to 30% of R′O (wherein R′ is Mg, Ca, Sr, Ba) represented by mol % in terms of oxides. According to PTL 3, it is considered that the vanadium phosphate-based glass shows fine fluidity at 500° C. or less and has no problems relating to the weather resistance that is inherent to phosphate glass.
PTL 4 (JP 2004-250276 A) discloses lead-free low melting point glass for sealing processing consisting of metal oxides of four components: 16 to 80% by weight of V2O5, 0 to 40% by weight of ZnO, 4 to 50% by weight of BaO and 0 to 60% by weight of TeO2. According to PTL 4, it is considered that the lead-free low melting point glass shows thermal properties that are comparable to those of low melting point glass comprising lead, and an excellent sealing performance.
PTL 5 (JP 2003-192378 A) discloses lead-free low melting point glass for sealing processing comprising 20 to 80% by weight of B2O3 as a mesh-forming oxide, 0 to 60% by weight of BaO as a mesh-modifying oxide, and 0 to 60% by weight of ZnO as an intermediate oxide, and a lead-free low melting point glass for sealing processing comprising 30 to 70% by weight of V2O5 as a mesh-forming oxide, 50 to 80% by weight of BaO as a mesh-modifying oxide, and 0 to 50% by weight of ZnO as an intermediate oxide. According to PTL 5, it is considered that the lead-free low melting point glass shows excellent properties that are comparable to those of PbO—B2O3-based low melting point glass.
PTL 6 (JP 2008-251324 A) discloses an electroconductive paste comprising, as a basic constitution, an organic medium comprising a dispersing agent, and frit glass comprising vanadium, phosphorus, antimony and barium and silver particles that are added into the organic medium, wherein the frit glass has a composition consisting of V2O5: 50 to 65 mass %, P2O5: 15 to 27 mass %, Sb2O3: 5 to 25 mass % and BaO: 1 to 15 mass % in terms of oxides, the silver particles comprise flaky particles and granular particles, wherein the flaky particles have an average particle size of 2 to 5 the granular particles have an average particle size of 0.1 to 3 μm, the incorporation ratio of the flaky particles and the granular particles is 50:50 to 90:10 by mass ratio, and the frit glass is contained by 5 to 30 mass % with respect to the silver particles. According to PTL 6, it is considered that a silver-based electroconductive paste that does not contain lead, bismuth and alkali metals as frit glass and is excellent in electroconductivity can be provided.
PTL 7 (JP 2006-332032 A) discloses a thick film electroconductive composition in which an electroconductive silver powder, a zinc-containing additive and a lead-free glass frit are dispersed in an organic medium. According to PTL 7, it is considered that a preferable glass frit comprises, as the oxide components in the glass composition, 0.1 to 8% by weight of SiO2, 0 to 4% by weight of Al2O3, 8 to 25% by weight of B2O3, 0 to 1% by weight of CaO, 0 to 42% by weight of ZnO, 0 to 4% by weight of Na2O, 0 to 3.5% by weight of Li2O, 28 to 85% by weight of Bi2O3, 0 to 3% by weight of Ag2O, 0 to 4.5% by weight of CeO2, 0 to 3.5% by weight of SnO2 and 0 to 15% by weight of BiF3.